diff --git a/CHANGELOG.md b/CHANGELOG.md
index 18724966..0c8adcc5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+## Unreleased
+
+- make `httpOnly`, `secure`, and `partitioned` two-state flags with `false` defaults
+- treat omitted flags and explicit `false` as the same value semantics
+- remove `CookieNullableField.httpOnly`, `CookieNullableField.secure`, and `CookieNullableField.partitioned`
+- migrate `copyWith(clear: {...})` call sites by dropping those removed fields and using omitted flags or explicit `false` instead
+
 ## 0.1.0
 
 - add `Cookie.validate` for explicit pre-serialization checks
diff --git a/README.md b/README.md
index 0dee6267..98baaa93 100644
--- a/README.md
+++ b/README.md
@@ -78,6 +78,11 @@ if (errors.isNotEmpty) {
 - `SameSite=None` requires `Secure=true`.
 - `Partitioned=true` requires `Secure=true`.
 
+## Flag Semantics
+
+- `HttpOnly`, `Secure`, and `Partitioned` are two-state flags.
+- Omitting a flag is equivalent to setting it to `false`.
+
 # API Reference
 
 See the [API documentation](https://pub.dev/documentation/ocookie) for detailed information about all available APIs.
diff --git a/lib/src/cookie.dart b/lib/src/cookie.dart
index ada6e9e1..e0086287 100644
--- a/lib/src/cookie.dart
+++ b/lib/src/cookie.dart
@@ -32,13 +32,10 @@ enum CookieSameSite {
 enum CookieNullableField {
   expires,
   domain,
-  httpOnly,
   maxAge,
   path,
   priority,
   sameSite,
-  secure,
-  partitioned,
 }
 
 class Cookie {
@@ -49,26 +46,26 @@ class Cookie {
     this.value, {
     this.expires,
     this.domain,
-    this.httpOnly,
+    this.httpOnly = false,
     this.maxAge,
     this.path,
     this.priority,
     this.sameSite,
-    this.secure,
-    this.partitioned,
+    this.secure = false,
+    this.partitioned = false,
   });
 
   final String name;
   final String value;
   final DateTime? expires;
   final String? domain;
-  final bool? httpOnly;
+  final bool httpOnly;
   final Duration? maxAge;
   final String? path;
   final CookiePriority? priority;
   final CookieSameSite? sameSite;
-  final bool? secure;
-  final bool? partitioned;
+  final bool secure;
+  final bool partitioned;
 
   Cookie copyWith({
     String? name,
@@ -100,17 +97,10 @@ class Cookie {
 
     assertNoConflict(CookieNullableField.expires, expires, 'expires');
     assertNoConflict(CookieNullableField.domain, domain, 'domain');
-    assertNoConflict(CookieNullableField.httpOnly, httpOnly, 'httpOnly');
     assertNoConflict(CookieNullableField.maxAge, maxAge, 'maxAge');
     assertNoConflict(CookieNullableField.path, path, 'path');
     assertNoConflict(CookieNullableField.priority, priority, 'priority');
     assertNoConflict(CookieNullableField.sameSite, sameSite, 'sameSite');
-    assertNoConflict(CookieNullableField.secure, secure, 'secure');
-    assertNoConflict(
-      CookieNullableField.partitioned,
-      partitioned,
-      'partitioned',
-    );
 
     return Cookie(
       name ?? this.name,
@@ -121,9 +111,7 @@ class Cookie {
       domain: clear.contains(CookieNullableField.domain)
           ? null
           : domain ?? this.domain,
-      httpOnly: clear.contains(CookieNullableField.httpOnly)
-          ? null
-          : httpOnly ?? this.httpOnly,
+      httpOnly: httpOnly ?? this.httpOnly,
       maxAge: clear.contains(CookieNullableField.maxAge)
           ? null
           : maxAge ?? this.maxAge,
@@ -134,12 +122,8 @@ class Cookie {
       sameSite: clear.contains(CookieNullableField.sameSite)
           ? null
           : sameSite ?? this.sameSite,
-      secure: clear.contains(CookieNullableField.secure)
-          ? null
-          : secure ?? this.secure,
-      partitioned: clear.contains(CookieNullableField.partitioned)
-          ? null
-          : partitioned ?? this.partitioned,
+      secure: secure ?? this.secure,
+      partitioned: partitioned ?? this.partitioned,
     );
   }
 
@@ -171,12 +155,12 @@ class Cookie {
     if (domain?.isNotEmpty == true && !cookieAllowPattern.hasMatch(domain!)) {
       errors.add('domain is invalid');
     }
-    if (sameSite == CookieSameSite.none && secure != true) {
+    if (sameSite == CookieSameSite.none && !secure) {
       errors.add(
         'SameSite attribute is set to none, but the secure flag is not set to true.',
       );
     }
-    if (partitioned == true && secure != true) {
+    if (partitioned && !secure) {
       errors.add(
         'Partitioned attribute is set, but the secure flag is not set to true.',
       );
@@ -202,11 +186,11 @@ class Cookie {
     if (domain?.isNotEmpty == true && !cookieAllowPattern.hasMatch(domain!)) {
       throw ArgumentError.value(domain, 'domain', 'domain is invalid');
     }
-    if (sameSite == CookieSameSite.none && secure != true) {
+    if (sameSite == CookieSameSite.none && !secure) {
       throw StateError(
           'SameSite attribute is set to none, but the secure flag is not set to true.');
     }
-    if (partitioned == true && secure != true) {
+    if (partitioned && !secure) {
       throw StateError(
           'Partitioned attribute is set, but the secure flag is not set to true.');
     }
@@ -217,8 +201,8 @@ class Cookie {
       if (domain?.isNotEmpty == true) 'Domain=$domain',
       if (path?.isNotEmpty == true) 'Path=$path',
       if (expires != null) 'Expires=${formatHttpDate(expires!)}',
-      if (httpOnly == true) 'HttpOnly',
-      if (secure == true) 'Secure',
+      if (httpOnly) 'HttpOnly',
+      if (secure) 'Secure',
       if (priority != null)
         'Priority=${switch (priority!) {
           CookiePriority.low => 'Low',
@@ -231,7 +215,7 @@ class Cookie {
           CookieSameSite.lax => 'Lax',
           CookieSameSite.none => 'None',
         }}',
-      if (partitioned == true) 'Partitioned',
+      if (partitioned) 'Partitioned',
     ];
 
     return parts.join('; ');
@@ -305,6 +289,14 @@ class Cookie {
       return value;
     }
 
+    bool parseFlagValue(String value) {
+      final normalized = value.trim().toLowerCase();
+      return switch (normalized) {
+        'false' || '0' || '?0' => false,
+        _ => true,
+      };
+    }
+
     final firstPair = parts.first;
     if (!firstPair.contains('=')) {
       throw ArgumentError.value(
@@ -330,9 +322,9 @@ class Cookie {
       cookie = switch (name.trim().toLowerCase()) {
         'expires' => cookie.copyWith(expires: parseExpiresValue(value)),
         'max-age' => cookie.copyWith(maxAge: parseMaxAgeValue(value)),
-        'secure' => cookie.copyWith(secure: true),
-        'httponly' => cookie.copyWith(httpOnly: true),
-        'partitioned' => cookie.copyWith(partitioned: true),
+        'secure' => cookie.copyWith(secure: parseFlagValue(value)),
+        'httponly' => cookie.copyWith(httpOnly: parseFlagValue(value)),
+        'partitioned' => cookie.copyWith(partitioned: parseFlagValue(value)),
         'path' => cookie.copyWith(path: value),
         'domain' => cookie.copyWith(domain: value),
         'samesite' => cookie.copyWith(
diff --git a/test/copy_with_test.dart b/test/copy_with_test.dart
index 88af7a2b..763f2bf9 100644
--- a/test/copy_with_test.dart
+++ b/test/copy_with_test.dart
@@ -55,25 +55,22 @@ void main() {
         clear: {
           CookieNullableField.expires,
           CookieNullableField.domain,
-          CookieNullableField.httpOnly,
           CookieNullableField.maxAge,
           CookieNullableField.path,
           CookieNullableField.priority,
           CookieNullableField.sameSite,
-          CookieNullableField.secure,
-          CookieNullableField.partitioned,
         },
       );
 
       expect(result.expires, isNull);
       expect(result.domain, isNull);
-      expect(result.httpOnly, isNull);
+      expect(result.httpOnly, isTrue);
       expect(result.maxAge, isNull);
       expect(result.path, isNull);
       expect(result.priority, isNull);
       expect(result.sameSite, isNull);
-      expect(result.secure, isNull);
-      expect(result.partitioned, isNull);
+      expect(result.secure, isTrue);
+      expect(result.partitioned, isTrue);
     });
 
     test('should throw when a field is set and cleared together', () {
@@ -107,5 +104,19 @@ void main() {
       expect(a, equals(b));
       expect(a.hashCode, b.hashCode);
     });
+
+    test('should treat omitted flags and false flags as equal', () {
+      final a = Cookie('sid', 'abc');
+      final b = Cookie(
+        'sid',
+        'abc',
+        httpOnly: false,
+        secure: false,
+        partitioned: false,
+      );
+
+      expect(a, equals(b));
+      expect(a.hashCode, b.hashCode);
+    });
   });
 }
diff --git a/test/from_string_test.dart b/test/from_string_test.dart
index cbbe8139..be12dc58 100644
--- a/test/from_string_test.dart
+++ b/test/from_string_test.dart
@@ -44,6 +44,66 @@ void main() {
       final cookie = Cookie.fromString('a="hello%20world"');
 
       expect(cookie.value, 'hello world');
+      expect(cookie.httpOnly, isFalse);
+      expect(cookie.secure, isFalse);
+      expect(cookie.partitioned, isFalse);
+    });
+
+    test('should preserve quoted values containing equals signs', () {
+      final cookie = Cookie.fromString('session="a=b=c%202"');
+
+      expect(cookie.value, 'a=b=c 2');
+    });
+
+    test('should ignore unknown attributes from real-world headers', () {
+      final cookie = Cookie.fromString(
+        'sid=abc123; Path=/; HttpOnly; Secure; SameSite=None; Foo=bar; Version=1',
+      );
+
+      expect(cookie.name, 'sid');
+      expect(cookie.value, 'abc123');
+      expect(cookie.path, '/');
+      expect(cookie.httpOnly, isTrue);
+      expect(cookie.secure, isTrue);
+      expect(cookie.sameSite, CookieSameSite.none);
+      expect(cookie.priority, isNull);
+    });
+
+    test('should keep the last repeated recognized attribute', () {
+      final cookie = Cookie.fromString(
+        'sid=abc; Path=/one; Path=/two; SameSite=Lax; SameSite=None; Secure',
+      );
+
+      expect(cookie.path, '/two');
+      expect(cookie.sameSite, CookieSameSite.none);
+      expect(cookie.secure, isTrue);
+    });
+
+    test('should treat non-standard flag values predictably', () {
+      final enabledCookie = Cookie.fromString(
+        'sid=abc; Secure=1; HttpOnly=true; Partitioned=?1',
+      );
+      final disabledCookie = Cookie.fromString(
+        'sid=abc; Secure=false; HttpOnly=false; Partitioned=false',
+      );
+
+      expect(enabledCookie.secure, isTrue);
+      expect(enabledCookie.httpOnly, isTrue);
+      expect(enabledCookie.partitioned, isTrue);
+      expect(disabledCookie.secure, isFalse);
+      expect(disabledCookie.httpOnly, isFalse);
+      expect(disabledCookie.partitioned, isFalse);
+    });
+
+    test('should ignore invalid recognized attribute values without failing',
+        () {
+      final cookie = Cookie.fromString(
+        'sid=abc; SameSite=invalid; Priority=urgent; Secure',
+      );
+
+      expect(cookie.sameSite, isNull);
+      expect(cookie.priority, isNull);
+      expect(cookie.secure, isTrue);
     });
 
     test('should throw for invalid first pair without equals', () {
@@ -90,5 +150,18 @@ void main() {
         'c=d',
       ]);
     });
+
+    test('should split combined headers with quoted commas and expires dates',
+        () {
+      final values = Cookie.splitSetCookie(
+        'a="b,c"; Path=/, sid=1; Expires=Wed, 21 Oct 2015 07:28:00 GMT; HttpOnly, theme=light',
+      );
+
+      expect(values, [
+        'a="b,c"; Path=/',
+        'sid=1; Expires=Wed, 21 Oct 2015 07:28:00 GMT; HttpOnly',
+        'theme=light',
+      ]);
+    });
   });
 }